Most current generation jet aircraft require that a pilot immediately command a rudder change (and/or an aileron change when in the air) following a sudden loss of thrust from an engine. Failure to respond immediately (within one second in the case of a takeoff roll) can result in a loss of aircraft control.
Some aircraft use a simple, limited authority engine-out control augmentation subsystem to assist a pilot in producing a rudder response command that compensates for the loss of thrust. Unfortunately, most such subsystems are functional only during the takeoff, landing and go-around phases of a flight. For example, the Model A320 aircraft produced by the European Commercial Airplane Manufacturing Consortium, commonly referred to as Airbus, includes a limited authority engine failure yawing moment compensation subsystem. The compensation subsystem is coupled to the rudder via a mechanical yaw damper control mechanism and is only operational during the takeoff, approach, landing and go-around phases of a flight. Although safety is slightly enhanced, such a limited authority engine failure subsystem has the disadvantage that it still requires that a pilot respond quickly to an engine failure.
Recent models of the 707-E6 manufactured by The Boeing Airplane Company, commonly referred to as the AWACS airplane, also have a limited authority outboard engine failure yawing moment compensation subsystem. The subsystem provides no compensation for inboard engine failures. Since the subsystem is operational only at airspeeds below 200 knots, it is primarily operational only during the takeoff, approach, landing and go-around phases of a flight. The subsystem was added to the 707-E6 design partially to compensate for the loss of yaw control resulting from the addition of the AWACS randome to the airplane. As with the A320 system, while a limited authority engine failure enhancement to a flight control system slightly enhances safety, such an enhancement still requires that a pilot respond quickly to an engine failure.
An experimental jet transport aircraft designed by The Boeing Company for the military several years ago, designated the YC-14, contained a subsystem that compensated for the loss of lift due to an engine shutdown. The subsystem commanded a reconfiguration of the flaps when an engine shutdown was detected. It did not assist in controlling the lateral-directional axis of the aircraft during an engine failure.
While several commercial aircraft contain a subsystem that detects an engine failure and displays the failure on the flight deck of the aircraft as a pilot caution or warning, such display subsystems do not directly assist a pilot in controlling the operation of the aircraft.
As will be better understood from the following description, this invention is directed to providing an engine-out control augmentation or enhancement subsystem for a flight control system that immediately and promptly assists the pilot of an aircraft and/or an automatic lateral-directional control subsystem in compensating for the yawing moments produced by differential engine thrust, i.e., produced by the loss of thrust of one or more engines on one side of the aircraft. In addition to increasing safety, the invention allows the size of the tail of an aircraft to be decreased.